9550

• UCREFRP Catalog Number: 9550
• Author: Snyder, D. E. and R. T. Muth.
• Title: Catostomid Fish Larvae and Early Juveniles of the Upper Colorado River Basin - Morphological Descriptions, Comparisons, and Computer-interactive Key.
• USFW Year: 2004.
• USFW - Doc Type: Fort Collins, CO.
• Copyright Material: NO

EARLY CLEAVAGE

Axi a 1 Strand
(bes t seen
from above)

Yolk under
thin yolk-sac
wi th ca vity
between

Germ Ri ng

MORULA

Yolk protruding
through Germ Ring GASTRULA

Yolk Plug with
protruding Periblast
Material

EARLY EMBRYOS

Fig. 2. Selected anatomical features of cypriniform fish eggs and embryos (from Snyder 1981; based on drawings
from Long and Ballard 1976).

Berry and Richards (1973) noted that
"although species of a genus may vary from one
geographical area to another, generally the larval
forms of closely related species look alike. At
the same time, larvae of distantly related forms
may be closely similar in gross appearance."
Cypriniform larvae as a group are distinctive
and generally easy to distinguish from larvae of
other families. Beginning workers should
become familiar with the general larval charac-
teristics of each family likely to be encountered.
The guides and keys cited in Snyder (1983b)
and Kelso and Rutherford (1996) are most use-
ful in this respect. Auer (1982) is particularly
recommended since it covers all families and
some species in the Upper Colorado River
Basin. The pictorial guide to families in Wallus
et al. (1990) and Kay et al. (1994) and discus-
sions of taxonomic characters by Berry and
Richards (1973) and Kendall et al. (1984) are
also recommended.

In the Upper Colorado River System,
cypriniform larvae are readily categorized as
cyprinids or catostomids. But elsewhere, if
members of the cyprinid subfamily Cyprininae
(carps) and the catostomid subfamily Ictiobinae
(carp suckers and buffalo fishes) or tribe Erimy-
zontini (chub suckers) are present, identification
at the family level can be more difficult.
Within their respective families, and espec-
ially at the subfamily level, cypriniform larvae
are very homogeneous in gross structure and
appearance. Accordingly, they may be espec-
ially difficult to discriminate at genus or species
levels. This is particularly true of Colorado
River System catostomids. For the latter, speci-
fic identification relies on size at which certain
developmental events occur, form of the gut,
melanistic (brown or black) pigment patterns,
osteological characters, and to a limited extent,
morphometrics and meristics (especially dorsal-
fin-ray counts for metalarvae and juveniles).

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